Recent news from the world of avgas has not been good and I believe that the parties involved have collectively painted themselves into a corner here. Let me explain:
This all started because the US Environmental Protection Agency is under pressure to get the tetra-ethyl lead out of aviation fuel. There is no doubt this has to happen as there is ample evidence that lead is a neurotoxin and its presence in avgas is causing measurable brain damage in children. It has to go away and soon and the EPA is going to make it go away soon, too. The debate is over what to replace it with.
Teledyne Continental Motors was concerned that no one was stepping up to the plate to act as a leader in this problem, so they have made a decision to go with 94UL fuel. 94UL is essentially 100LL with the lead removed. It can be produced today very easily and for probably about the same price as 100LL. The only problem is that while about 80% of the existing engines out there can run on it, that leaves about 20% that can't. 94UL would be great for the engines that were designed for the old 80-87 avgas as the lead in 100LL is hard on them and they don't need the octane. Continental's response to the 20% of owners of aircraft that can't use 94UL is that there will be kits to lower compression ratios to continue to use existing engines, but probably with lower gross weights to compensate. Owners will also be able to upgrade to larger engines, for instance trading in an old Continental O-470 for a Continental O-520 to maintain horsepower.
Textron Lycoming has responded by rejecting 94UL and betting on 100 unleaded instead. One form of 100 unleaded is G100UL which is being developed by General Aviation Modifications and is intended to be a new fuel developed from existing refinery products that will replace the lead with other more exotic, but safer, compounds. Some aircraft type clubs, representing high-powered engine aircraft owners, including the American Bonanza Society, the Malibu Mirage Owners and Pilots Association and the Cirrus Owners and Pilots Association have formed the Green 100 Octane Coalition to advocate for a 100 octane solution over 94UL as they believe that anything less will ground their aircraft. The downside of G100UL is that right now it looks like it will cost quite a bit more at the pumps than 94UL would or than 100LL currently does, perhaps double. This fuel would be usable by all present piston aircraft.
There are also some advocates who say "why not make both 94UL and 100UL?"
Unfortunately I think all of these approaches are dead ends.
Lycoming has a good point in its arguments against 94UL, indicating that the loss of power with 94 octane fuel will severely limit the solutions for more powerful aircraft. Lycoming's General Manager Michael Kraft stated in June 2010 that 94UL would be a mistake that could cost the aviation industry billions. The aircraft type clubs note that while the aircraft that need 100 octane are only 20% of the fleet, they buy 80% of the avgas and that if they are sacrificed that the remaining fuel sales will not be enough to keep the airports open and that the result will be a collapse of general aviation as not economically sustainable.
The main problem with G100UL is the cost. 100LL avgas is currently about $1.30 per litre in the Ottawa area. Look for G100UL to start out at about double that and go up from there as the effects of the Deepwater Horizon disaster and the global flat production of oil in the face of increasing demand bring on more high gas prices. In 2008 the US price of avgas hit about $7 per gallon and it seriously curtailed flying at that price. I think that an initial price of about $10 per US gallon is a non-starter for G100UL, but it is likely to cost about that at first and only go up from there. Those kind of prices will seriously hurt general aviation as quickly as the 94UL solution will. That makes neither a good answer to the lead dilemma.
The solution of "why not make both?" is also a non-starter. Airports are today equipped with just one avgas tank. Stocking two grades of avgas would require a huge investment in fuel tanks and pumps and that is just not going to happen. The other side of the coin is that avgas is essentially a very niche market item, the refiners are not going to want to make and distribute more than one kind.
This entire leaded fuel issue has been completely ignored by the aviation industry for more than twenty years, as they were all hoping it would just go away. It hasn't gone away and now the regulators are forcing change in a hurry when long-term planning should have been done by the aviation industry decades ago. Rather than letting the engine manufacturers fight over this issue, we need a single forum where the pilot groups, type clubs, engine and airframe makers can all get together with the regulators, including TC, the FAA and ASTM who control the fuel specs, and work out a solution that won't exclude lots of aircraft and drive people out of flying and also won't greatly increase costs and also drive people out of flying.